Fermi Sees a Nova
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- Visualizations by:
- Walt Feimer
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NASA's Fermi Gamma-ray Space Telescope has detected gamma-rays from a nova for the first time. The finding stunned observers and theorists alike because it overturns a long-standing notion that novae explosions lack the power for such high-energy emissions.
In March, Fermi's Large Area Telescope (LAT) detected gamma rays — the most energetic form of light - from the nova for 15 days. Scientists believe that the emission arose as a million-mile-per-hour shock wave raced from the site of the explosion. A nova is a sudden, short-lived brightening of an otherwise inconspicuous star. The outburst occurs when a white dwarf in a binary system erupts in an enormous thermonuclear explosion.
"In human terms, this was an immensely powerful eruption, equivalent to about 1,000 times the energy emitted by the sun every year," said Elizabeth Hays, a Fermi deputy project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "But compared to other cosmic events Fermi sees, it was quite modest. We're amazed that Fermi detected it so strongly." More information here.
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Credits
Please give credit for this item to:
NASA/Conceptual Image Lab/Goddard Space Flight Center
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Animator
- Walt Feimer (KBR Wyle Services, LLC) [Lead]
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Writer
- Francis Reddy (University of Maryland College Park)
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Producer
- Scott Wiessinger (KBR Wyle Services, LLC)
Missions
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ID: 11641 Produced Video
Cosmic Blast
Read moreA nova is a sudden, short-lived explosion from a compact star not much larger than Earth. The outburst comes from a collapsed star known as a white dwarf, which circles so close to a normal star that a stream of gas flows between them. This gas piles up into a layer on the white dwarf's surface until it reaches a flash point and detonates in a runaway thermonuclear explosion. Astronomers estimate that between 20 and 50 novae occur each year in our galaxy, but despite their power most go undiscovered. NASA’s Fermi Gamma-ray Space Telescope has observed several nearby novae and found that each blast produces gamma rays, the most energetic form of light. Scientists think the gamma rays result from collisions among multiple shock waves that race from the site of the explosion in a rapidly expanding shell of debris. Watch the video to see an animation of a nova eruption. ||
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ID: 11608 Produced Video
Fermi Reveals Novae as a New Class of Gamma-Ray Sources
Read moreObservations of four stellar eruptions, called novae, by NASA's Fermi Gamma-ray Space Telescope firmly establish that these relatively common outbursts nearly always produce gamma rays, the most energetic form of light. A nova is a sudden, short-lived brightening of an otherwise inconspicuous star caused by a thermonuclear explosion on the surface of a white dwarf, a compact star not much larger than Earth. Novae occur because a stream of gas flowing from the star continually piles up into a layer on the white dwarf's surface. This layer eventually reaches a flash point and detonates in a runaway thermonuclear explosion. Each nova releases up to 100,000 times the annual energy output of our sun. Prior to Fermi, no one suspected these outbursts were capable of producing high-energy gamma rays. Such emission, with energies millions of times greater than visible light, usually is associated with far more powerful cosmic blasts.Fermi's Large Area Telescope (LAT) scored its first nova detection in March 2010 with an outburst of V407 Cygni. In this rare type of system, a white dwarf interacts with a red giant star more than a hundred times the size of our sun. Other members of this unusual stellar class have been observed to "go nova" every few decades.In 2012 and 2013, the LAT found three much more typical, or "classical," novae: V339 Delphini in 2013 and V1324 Scorpii and V959 Monocerotis in 2012. The outbursts occurred in comparatively common systems where a white dwarf and a sun-like star orbit each other every few hours. Astronomers estimate that between 20 and 50 novae occur each year in our galaxy. Most go undetected, their visible light obscured by intervening dust and their gamma rays dimmed by distance. All of the gamma-ray novae found so far lie between 9,000 and 15,000 light-years away, which is relatively nearby compared to our galaxy's size.One explanation for the gamma-ray emission is that the blast creates multiple shock waves, which expand into space at slightly different speeds. Faster shocks could interact with slower ones, accelerating particles to near the speed of light. These particles ultimately could produce gamma rays. ||
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